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Desertdog
19-02-2016, 05:28 AM
I have a 31/2 ton reciprocating Copeland R22 unit.

I read 20 amps full load apparent amps not true RMS. Saving up for a Better clamp on meter.

So would a power factor of 0.95 get me to true amps.

This compresor was new 2 years ago.

chilliwilly
19-02-2016, 06:02 PM
Are you in North America or Europe, ie is it running on 120, 240, 270, 415, or 480v, 60 or 50 hz? Is the compressor healthy, you say that the compressor is only 2 years old, what is the insulation reading on the windings?

Its my understanding that all meters read RMS, otherwise 240/230 volt would be recorded as peak value (1.41 x 240 = 338 volts), as you know it all depends on the quality of the meter.

Knowing the P.F; of a fixed load would give you the true power of that load and similarly, KW/KVA = PF, KVA x PF = KW, KW/PF = KVA; but why are you interested in true RMS?

xxargs
20-02-2016, 11:46 AM
Most digital multimeter (without 'true RMS' sign) assume measure sinusoid shape voltage and current without distortion - if distorted (flatten top of half period on voltage, high peak current around 15-30 degree on period top and non current rest of half period ) or square-wave, they measure (very) wrong value.

Current side is now days much worse to measure compare to Voltage-side ie. connected to rectify-bridge with more or less working PFC-circurit in electronic drivers to compressor, switched power supply etc. with high degree of distorted sinus shape, almost spike pulses now...

And for measure cos(fi) you must measure voltage and current same time with more advanced instrument to measure phase difference between voltage and current. And measure PF (effect of cos(fi) included in this value) from electronic drivers, switched power supply etc. with heavy non sinus, disordered current need more advanced instruments with high rate sampling on current and voltage same time and do same maths as modern electronic billing electricity meter.

BradC
20-02-2016, 01:39 PM
Hope it will help.
http://www.hvacrinfo.com/cope_ae_bulletins/TAE1249.PDF

That is gold! Thankyou. I have an R22 ducted heat pump and I've replaced the condenser with a BPHX and dropped the SCT to 25C from about 50-60, and as a result the power factor has dropped to about .55, and this is exactly what I've been looking for. Off top buy some caps.

chilliwilly
20-02-2016, 01:51 PM
The other poster must have a really cheap and nasty meter then, all meters that I've ever had are very accurate. That's probably why I can't see why he's having a problem.